Chemical Tests
Lesson 15
Testing Household Liquids with Red Cabbage Juice
Students use red cabbage juice and a reading selection to learn about acids, bases and neutrals.
3. Lesson set up and Management
GLE 1.1.1 Understand how to use properties to sort natural and manufactured materials and objects.
GLE 2.1.1 Understand how to ask questions about objects, organisms and events in the environment.
(3) Recognize the question being answered in an investigation.
GLE 2.1.2 Understand how to plan and conduct simple investigations following all safety rules.
GLE 2.1.3 Understand how to construct a reasonable explanation using evidence.
GLE 2.1.5 Understand how to report investigations and explanations of objects, events, systems and processes.
GLE 2.2.1 Understand that all scientific observations should be reported accurately and honestly even when the observations contradict expectations.
GLE 2.2.3 Understand why similar investigations may not produce similar results
GLE 2.2.4 Understand how to make the results of scientific investigations reliable.
- Students will get to go through the inquiry process with nine household liquids.
- Students will run the cabbage test, record their data, and examine their data and information from a reading source.
- Students will reach a conclusion to the question, "is each liquid an acid, base or neutral?"
3. Lesson set up and Management
Materials:
- It is a big time saver to make 15 new mats for this activity ahead of time. Use a Blackline Master – Test Mat for Five Unknowns (reverse), label each circle with the name one of household liquids, and draw one more small circle on to use as the compare (control) circle. Make 15 copies and laminate to use year after year.
- Use the "Check Your Science Pail" poster board for quick student reference. Add "hand lens" and "black paper."
- Signs with each material and the amount needed to be picked up at the materials center are helpful.
- If your cabbage juice is green, add vinegar to it a drop at a time until it is blue-purple.
- If your cabbage juice is pink, add baking soda, a pinch at a time until it is blue-purple.
- Test your cabbage juice before the lesson with baking soda (blue unknown) and alum (yellow unknown) to make sure it is working properly. The Baking soda should turn green and the alum should turn a darker/brighter purple. If it is not working properly, you will need to make a fresh batch following the directions in the manual or request a fresh batch from your district materials center.
Student Management:
- This lesson can be divided between two days.
- Review safety rules carefully with students.
- Assign one partner to be the materials manager and have that student pick up the materials from the materials center after you model how to do it.
- PREPARATION #5
- Make a table that resembles Record Sheet 15-A and laminate it for use year after year.
- PROCEDURE #3
- Have a transparency of Record Sheet 15-A ready to show students and model how to use it correctly.
Writing Support:
- Students record their test results on Record Sheet 15-A. They can respond to the following questions in their science notebooks:
- How did the original 5 unknowns react with the red cabbage juice?
- Using what you just learned about acids, bases and neutrals, what can you know say about the original five unknowns?
- Where would you put each unknown on the class board of acids, bases and neutrals?
Reading Support:
- Students read "The Case of the Disappearing Stomachache" to help them learn about acids, bases and neutrals.
Math Support:
- Students can create an acid-base continuum by creating a box with three sections. Have them measure each section 1inch tall x 3 inches long. Label first box acid, middle box neutral and last box base. They can then color moving from pink to purple to green.